The present invention relates to a high-frequency device, such as a phased array antenna, for transmitting high-frequency signals, which is used to transmit and receive high-frequency signals such as a microwave, and relates to a method of manufacturing the same. More particularly, the invention relates to a high-gain high-frequency device which can be applied to a high-frequency band and which has such a switch having movable parts as a micromachine switch, and relates to a method of manufacturing the same.
Conventionally, a phased array antenna which is used as a vehicle-installed satellite tracing antenna or a satellite-installed antenna, and in which a large number of radiating elements are disposed is proposed in, for example, The Institute of Electronics, Information and Communication Engineers Technical Report No. AP 90-75, and Japanese Unexamined Patent Publication No. 1-290301.
This type of phased array antenna has a function for arbitrarily varying the direction of a beam by changing the phase of feeding power to each radiating element.
As means for varying the phase of feeding power is generally used a digital phase shifter (hereinafter, abbreviated as a phase shifter) composed of a plurality of phase-shifting circuits each having a different fixed amount of phase shift. In the phased array antenna, each phase-shifting circuit is turned on or off by a 1-bit digital control signal and the amount of phase shift in each phase-shifting circuit is combined with each other. By combining the amount of the phase shift, power-feeding phases of 0 to 360xc2x0 can be obtained in the whole phase sifter
Particularly, in the conventional phased array antenna, a large number of semiconductor elements such as a PIN diode and a GaAsFET are used as switching elements in each phase-shifting circuit, and a large number of driving circuit parts are used to drive such elements. The phase shifter has a structure for generating a predetermined amount of phase shift by applying a direct current or a direct voltage to the switching elements to turn on/off, and by varying the length of a transmission path, susceptance, a reflection coefficient, and the like.
On the other hand, recently, high-data-rate communication is required in the field of low-Earth-orbiting satellite communication, because of an increase in the use of the Internet, and wide spread use of multimedia communication. Accordingly, it is required to obtain a high-gain antenna. Also, it is required to increase a transmission bandwidth in order to achieve communication at a high data rate. Furthermore, because of a deficiency of frequency resources at a low frequency band, it is required to rapidly realize an antenna which can be applied at a high-frequency band of Ka band (20 GHz or more).
Specifically, as an antenna of a low-Earth-orbiting satellite tracing terminal at a ground station, the following technical performances are required:
Frequency: 30 GHz
Isotropic gain of the antenna: 36 dBi
Beam scanning range: Beam tilt angle of 50xc2x0 from the front
In order to achieve the above by a phased array antenna, first, an opening area of about 0.13 m2 (360 mmxc3x97360 mm) is required. Moreover, in order to reduce side lobes, it is necessary to avoid the generation of grating lobes by arranging radiating elements at intervals of about xc2xd wavelength (about 5 mm at 30 GHz).
Also, in order to divide a beam scanning step into a number of steps and to reduce the degradation of side lobes arising from a quantization error of the digital phase shifter, it is preferable that phase-shifting circuits used for each phase shifter be of 4 bits. (minimum bit phase shifter of 22.5xc2x0 or more.
The total number of radiating elements and the bits of the phase-shifting circuits which are used for a phased array antenna that satisfies the above conditions are as follows:
The number of phase-shifting circuit elements: 72xc3x9772=about 5000.
The number of bits of phase-shifting circuits: 72xc3x9772xc3x974=about 20000 bits.
Here, when a high-gain phased array antenna which can be applied to such a high-frequency band is achieved by the aforesaid conventional art, for example, a phased array antenna disclosed in Japanese Unexamined Patent Application Publication No. 1-290301, which is shown in FIG. 1, the following problems are posed:
In such a conventional phased array antenna, since individual phase-shifting circuits in each phase shifter 13 are controlled by one driver circuit 12 formed on a driving circuit substrate 11, as shown in FIG. 1, it is necessary to connect the driver circuit 12 with all the phase-shifting circuits individually. Accordingly, the number of wires for connection is required to correspond to a value obtained by the expression: the number of radiating elementsxc3x97the number of bits of phase-shifting circuits. When the aforesaid values are applied, the number of wires for each phase-shifting circuit (4 bits) of one row (72 radiating elements) in a radiating-element array of 72xc3x9772 is obtained by the equation, 72xc3x974=288.
When such a wiring is formed on the same plane, even when the equation, the width (L) of wiring+the space (S) of wiring=50 xcexcm+50 xcexcm=0.1 mm, is satisfied, the width of bundle wires of one row (72 of radiating elements) is obtained by the equation, 0.1 mmxc3x97288=28.8 mm.
On the other hand, in the phased array antenna which can be applied to a frequency of 30 GHz, the radiating elements are required to be arranged with a space of about 5 mm; as described above. However, in the conventional art, the width of the bundle wires is as long as 28.8 mm, as described above, which is significantly thick, so that it is physically impossible to arrange them.
In this case, when not only layers (a radiating element substrate 21 and a parasitic element substrate 31) in which the radiating elements 22, 32 are formed, but also a distribution/combination device 14 and the phase shifters 13 are each formed on a different layer, only the phase shifters 13 can be freely arranged on a layer on which the phase shifters 13 are to be formed. Consequently, the aforesaid problems of arrangement can be solved. Accordingly, with a multilayer structure, a phased array antenna which is more applicable to a high-frequency band can be achieved. With such a multilayer structure, since the thickness of each layer is so small as to be a few millimeters, it is not so thick. Thus, the phased array antenna can be of a small area, so that it is particularly advantageous to install on a satellite or the like.
In the aforesaid high-frequency device, it has been examined to use a micromachine switch which is a micro mechanical switching element as a switching element used for switching an amount of phase shift in the phase shifter. However, with the foregoing multilayer structure, conventionally, since the space between the layers was filled with a dielectric substance, the micromachine switch having movable parts could not be used for the phase shifters formed on a layer arranged in between.
In other words, conventionally, when the high-frequency device such as a phased array antenna has multilayer structure, since the micromachine switch cannot be used as a switching element used in the phase shifters, it is not preferable.
The present invention is made to solve the above problems, and i is an object of the invention to provide a high-gain high-frequency device, such as a phased array antenna, which is applied to a high frequency band, and which can use such a switch having movable parts as a micromachine switch, and to provide a method of manufacturing the same.
The present invention relates to a high-frequency device including a substrate, a plurality of waveguides, a switch, a structure, a coupling layer, a separating layer, high-frequency parts, and control means, which will be described below. The substrate is made of a dielectric substance, and the plurality of waveguides is formed on the dielectric substrate and carries high-frequency signals. The switch has movable parts for switching connections of the waveguides formed on the substrate. The structure is disposed on the substrate and has a space above the area where the switch is formed. The coupling layer is made of a conductive material, is formed on the structure, and has coupling means for coupling the high-frequency signals on a predetermined area of the waveguides. The separating layer is made of a dielectric material formed on the coupling layer. The high-frequency parts are formed on the separating layer, in which the high-frequency signals are coupled between it and the waveguides via the coupling means. The control means controls the operation of the switch. As configured above, the switch can perform the operation of connection/disconnection in the space of the structure by being controlled by the control means.
In such a configuration, the structure may be made up of a plurality of spacers. At that time, the spacers may be made of a dielectric substance and may be disposed at the part of the coupling means. Also, the spacers may be formed of a conductive substance and may be arranged such that they are insulated from the waveguides. The structure may be formed of an integrated plate having a space therein. Also, a phase shifter may be formed of the waveguides and switches. In this case, the high-frequency parts are formed of radiating elements and the waveguides have a distributor for introducing a desired high frequency, thereby configuring a high-frequency device such as a phased array antenna.
In the process of manufacture according to the present invention, first, the plurality of waveguides for carrying the high-frequency signals on the dielectric substrate is formed. In the step, the switch having the movable parts for switching connections of the waveguides of the phased array antenna is formed on the substrate. Also, in the step, the structure having a space above the area at which the switch is formed is formed on the substrate. The coupling layer made of a conductive material and having the coupling means for coupling the high-frequency signals is formed on the structure such that the coupling means is placed on a predetermined area of the waveguides. Next, the separating layer made of a dielectric material is formed on the coupling layer. Also, the high-frequency parts in which the high-frequency signals are coupled between them and the waveguides via the coupling means are formed on the separating layer. The control means for controlling the operation of the switch is formed.
Accordingly, a state in which the switch having the movable parts controlled by the control means performs the operation of connection/disconnection is created.
Another high-frequency device according to the present invention includes an inner layer substrate forming a multilayer substrate, a plurality of waveguides, a switch, and a structure. The plurality of waveguides is formed on a main surface of the aforesaid inner layer substrate and carries high-frequency signals. The switch has movable parts for switching connections of the waveguides formed on the main surface of the inner layer substrate. The structure is disposed between the main surface of the inner layer substrate and a substrate disposed thereon and has a space above the switch-formed area.
As constructed above, the switch having the movable parts preforms the operation of connection/disconnection in the space of the structure. It is desirable to form the structure with a plurality of spacers. Also, it is preferable that the spacers be made of dielectric substance and may be disposed at the part of the coupling means. On the other hand, the spacers may be made of a conductive substance and may be arranged such that they are insulated from the waveguides. The structure may be made of an integrated plate having a space formed therein.